Sulfurization of di-isobutylene



3 Sheets-Sheet l Filed Feb. l5, 1951 l l dillo INVENTORS. .Sfere/z5 @/rz/ .Samva/C1 Cnam/O.

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NOV. 10, 1953 D. R. STEVENS ET AL SULFURIZATION OF DI-ISOBUTYLENE 5 Sheets-Sheet 5 Filed Feb. l5, 1951 INVENTORS a/va// Svrezrs na/ Patented Nov. l0, 1953 UNITED STATES PATENT UFFICE SULFURIZATION OF DI-IS OBUTYLENE Donald R. Stevens, Wilkinsburg, and Samuel C. Camp, Gibsonia, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a

corporation of Delaware Application February 15, 1951, Serial No. 211,078

6 Claims. (Cl. 260-327) This invention relates to the sulfurization of di-isobutylene and more particularly to an improved process for preparing a sulfurization product of di-isobutylene comprising compounds having the empirical formula Cal-11283 by the reyields of the desired sulfurized products are obtained with more economical use of di-isobutylene.

rlhe desired products of our invention comprise two isomeric compounds` having the empirical formula CsHizSa. orange-colored crystalline solid having a melting point of about 87 C. and the other is a yellowishorange crystalline solid having a melting point of about 80 C. The desired product may comprise either of these compounds alone or a mixture of them or the crude sulfurization product of which these isomers are constituents. The isomer having the higher melting point is believed to be 4-neopentyl-1,2-dithia-4-cycyopentene-S-thione having the structural formula:

The isomer having the lower melting point is believed to be 4-methyl-5-tert-buty1-1,2dithia 4cyclopentene3thione having the structural formula:

These products of our process have a number of important uses, among which may be mentioned their utility as chemical intermediates in the preparation of organic acids and as valuable additives for certain hydrocarbon fuels and cutting oils. The crude sulfurization product containing one or both of the isomers is a valuable component of superior cutting oils and is also useful as a cetane number improver for diesel fuels.

The equation for the sulfurization of di-iscbutylene 'which produces the products of our in- One of these isomers is an l.

2 VentOn iS CsHie-l-5S-)C3H12S3-F2H2S. Thus it may be seen that hydrogen sulfide is formed in the reaction. We have discovered that the hydrogen sulfide has an important effect on the course of the reaction. The hydrogen sulfide can react with unreacted di-isobutylene charge according to the followingrequation:

thus forming undesirable mercaptans and-lowering the yield of the desired C'al-IizSs products by consuming some of the di-isobutylene charge. Also the mercaptans so produced can react with unreacted sulfur forming undesirable disuldes and polysulfdes and also lowering the yield of the desired product by consuming a portion of the sulfur.

Our invention comprises a process for sulfurizing di-isobutylene in which the undesirable side reactions described above are largely avoided and the desired products are obtained in very high yields and high purity. In accordance with your invention in sulfurizing di-isobutylene the diisobutylene is charged beneath the Vsurface of a liquid reaction mass comprising molten sulfur, and hydrogen sulfide formed in the resulting reaction is removed from contact with the reaction mass substantially as rapidly as formed.

In a more specific embodiment our invention in sulfurizing di-isobutylene comprises charging diisobutylene beneath the surface of a liquid reaction mass comprising molten sulfur maintained at a temperature of between about 200 and 230 C. and a pressureof between about 25 and 120 pounds per square inch whereby hydrogen sulde is formed in the resulting reaction and removing hydrogen sulde from contact with the reaction mass substantially as rapidly as formed.

Our invention will be further described with reference to the accompanying drawings in which: i

Figure 1y shows diagrammatically one form of apparatus suitable for use with our process,

Figure 2 shows curves which plot data obtained in test runs of our process, and l Figure 3 shows diagrammatically a Vmodified form of apparatus suitable for use process. Y i Referring to Figure 1` of the drawing, there is shown a reaction vessel I provided with a stirrer 2, a feed inlet 3 located near the lower end of the reaction-vessel, and a gas outlet. 4 located near the upper end of vthe reaction vessel. InV a .preferred embodiment of our process, reaction vessel With our n I is charged with a mass of sulfur which is heated by heating means not shown in the drawing to a molten state and is maintained at a temperature of preferably between about 200 and 230 C. during the reaction. Di-isobutylene is pumped from supply tank 6 through pump i and line 3 into the reaction vessel .beneath thesurface of the mass of molten lsulfur therein. The di-isobutylene may be preheated before charging to the reaction vessel if desired, and if so a preheater can conveniently be placed between pump 'I and the reaction vessel. Agitatio'n -of the reaction mass is provided by stirrer 2 to insure proper ccntact and distribution of the reactants. The initial pressure in the reactor may be atmospheric or super-atmospheric, but preferably should be sufficient to maintain the di-isobutylene in the liquid state.

Upon contact between the di-isobutylene 'and molten sulfur under :these conditions, reaction voccurs rpredominantly accordingly to the equation CsHis-kJS-CaI-izSs--Z'Hzs. The hydrogen sulfide formed bubbles upwardly through the molten sulrur. Valve 8 in line Il is kept closed until a desired pressure of between about 25 and 120 pounds per Asquare inch vgage is built up within the reactor. (When pressures .are reerred to in the specification and claims, it will be understood lthat gage pressures are intended unless otherwise indicated.) When this desired pressure of between about 25 and 120 pounds per square inch is obtained, Valve S is opened to release at least part of the hydrogen sulfide from reaction Vessel I through line li and to maintain the pressure -in the reaction vessel `at the desired point. As a result of the release of hydrogen sulde from `the reaction vessel and introduction of -the di-isobutylene beneath the surface of 'the sulfur, contact between the unreacted di-isobutylene and hydrogen sulfide is kept to a desired minimum` Consequently there is little or no lower-ing of yield and purity of product caused by side reactions of the hydrogen sulde.

To further reduce the contact'between the hydrogen sulfide and '-the'di-isobutylene, Vthe hydrogen sulfide may be swept lout of the react-ion mass by an inert gas such as nitrogen, carbon dioxide, etc., which may be blown into the bottom reactor I through line 9. Passing lan 'inert gas through the reaction mass helps remove hydrogen suliide from the reaction mass `and also provides a relatively `Ihigh 'partial pressure of inert gas above the reaction rmass thus considerably diminishing 'the opportunity -for reaction between the di-iso'butylene `and hydrogen sulfide.

The hydrogen sulde 'removal line 4 can `be provided with a condenser between the reaction vessel I and 'the pressure control valve '-8 such as condenser I0 shown in the drawing. Di-isobutylene carried along by 'the-hydrogen suliide gas is condensed in this condenser I0 under 'the reaction pressure and flows back into the 'reactor I.

Another condenser lcan 'be provided beyond valve 8 such as condenser I I shown in -the drawing to condense any -di-isobutylene remaining in the hydrogenvsulde gas. Di-isobutylenelcondensed in condenser II can be returned to rthe di-isobu-tylene Ysupply tank through line I2 land pump I3 while hydrogen sulfide `is vented to the atmosphere or passed to suitable collecting means through line Il.

The reaction system is provided with suitable CII means for measuring temperature and pressure. Thus, as shown in the drawing, a pressure gage I5 is installed in the line between condenser I0 and valve B and the reactor I is provided with a thermal well I6 containing temperaturemeasuring means, not shown.

An amount -of di-isobutylene somewhat in excess of the stoichiometric amount of y1 mol per 5 mols of sulfur is charged to the reactor I over a charging period the length of which is governed by several considerations. The lower limit for the length of this charging period is determined by the practical limitations on the rate at which the particular amount of di-iso- :butylene may be charged for any particular diameter feed inlet, any particular pump size, etc. Also the charging period must be of suflicient length to avoid Vaporizing di-isobutylene from the hot reaction mass which might occur if the rate of charging is too rapid. The maximum length for the charging period is governed by the desirability of completing the react-ion fas rapidly as possible for the particular conditions of temperature and pressure. Thus vthe cli-isobutylene should be added to the reactor at least substantially as rapidly as it is consumed in the reaction although if for any reason it is not an object .-to iinish the reaction Yas rapidly as possible the di-isobutylene may be added .as slowly as desired. A charging period of from about l0 to about 60 minutes has proved to be very satisfactory when conducting the process under conditions comparable -to those recited in the example described below. However, a longer or `shorter charging -period may be used, bearing in mind the various considerations mentioned above.

The reaction between di-isobutylene and sulfur under the lconditions of our process is relatively slow and consequently the reactants should be maintained in Acontact for -Aa period vafter the charging yof di-isobutylene is completed in order to allow the reaction to go to completion and obtain the maximum lyield of the desired product. In general, it may be said that the yield of the desired CBI-liess products increases as the length of the reaction period is increased. However, we have found that after a certain length vof time the increase in yield for any given additional length of time becomes so small that the expenditure of time is not suiiiciently repaid by increase in yield. This condition is illustrated graphically by curve A in Figure 2 of ethe drawing.

`Curve A plots the reaction time in minutes against the yield of 'CaHizSa in 'per cent. The data were obtained by sulfurizing di-isobutylene according to our process 'at a temperature of 210 C. and a pressure of 60 pounds per square inch in a manner ysimilar 'to that described in the example below. In the tests on which curve A is based, there was a 30-minute period for charging di-isobutylene, and the reaction was permitted to continue for a total of 240 minutes after the end of the charging period. 'From curve A it is seen that the yield increases -continually for about 1'50 minutes. After this time the increase in yield'becomes slight and usually it would not be profitable to continue the reaction much beyond this 15G-minute period which is minutes after the 13G-minute chargingfperiod used in these tests.

The l'engthof the reaction period following 'the charging period will, of course, depend to some extent upon the length of the charging period.

acts-,90o

Thus if the charging period is very long most of the di-isobutylene in the reactor willhave already been incontact with'the sulfur for a long period of time before the charging period is completed and therefore the additional time after the end of the charging period for allowing the sulfur and di-isobutylene to react may be correspondingly shortened. Likewise if the charging period is short, the reaction period following the charging period must be correspondingly lengthened to obtain the maximum yield.

During the reaction period hydrogen sulfide is formed at a varying rate. Thus, during the first part of the reaction period while di-isobutylene is being charged, the rate of formation of hydrogen sulfide is fairly slow but becomes steadily more rapid and sometime after the charging of di-isobutylene is completed it reaches a maximum point after which it decreases sharply. The sharp decrease in the rate of hydrogen sulfide formation does not, however, indicate that complete reaction has occurred. A considerable increase in the CsHizSs products is obtained by allowing the reaction to continue afterthe rate of hydrogen sulfide formation decreases sharply. This characteristic of the reaction is illustrated in curve B of Figure 2.

In curve B the length of the reaction period in minutes is plotted against the cumulative volume of hydrogen sulfide released from the reaction vessel during the process. Curve B is based on data obtained in the sulfurization of di-isobutylene according to our process at a temperature of 210 C. and a pressure of 25 pounds per square inch. A di-isobutylene charging period of 46 minutes was used. It may be seen from curve B that the amount of hydrogen sulfide formed in the reaction increasesrapidly until about 60 minutes after the start of the charging period. At this point the rate of increase of hydrogen sulfide formation breaks sharply and from that point onward only a small additional amount of hydrogen sulfide is formed. Curves A and B are drawn on common axes to permit a convenient comparison of their results. It may be seen that the point of sharp decrease in hydrogen sulfide formation in curve B does not correspond with the point of substantially maximum yield of CsHizSa products in curve A. Thus, from the curves it may be concluded that the reaction should be permitted to continue for a considerable period after the sharp break in hydrogen sulfide formation occurs in order to obtain maximum yields.

With all of the above-mentioned factors in mind it can be concluded that the reaction should be continued for a period following the charging period and this reaction period should extend at least to the time at which the rate of formation of hydrogen sulfide becomes very slow if it is desired to obtain the highest yields of CsHizSa compounds. Preferably, this period should extend for a substantial period, for example from 5 to 60 minutes or more, after the rate of hydrogen sulfide formation becomes very slow.'V In a preferred embodiment of our process such as practiced in obtaining the data for curve A- of Figure 2 and in the example below, the total time for the reaction including both the charging period and the reaction period thereafter is from about 90to about 180 minutes. factory results may be obtained using shorter or advantageous where purity is important. For

However, satislonger periods, depending on the various factors '6 say 120 minutes after the end of a 30minute diisobutylene charging period, the crude reaction product is removed from the reactor and may be used for any purpose for which the crude product is suitable such as for adding to fuels or lubricants. However, it is frequently desirable to obtain the CsHizSa compounds in a more nearly pure condition. In such a case the crude reaction product can be subjected to purification 4procedures to obtain products such as a partially purified product,V a purified mixture consisting essentially of the two isomers of CsHizSs, or either of the pure compounds of Cal-11233. Of these possible alternatives, the partially purified product is favored for many commercial usages as a compromise between the more expensive pure compounds and the crude reaction product containing unreacted sulfur.

' To obtain the product which we call the partially purified product, the crude reaction product is treated with a suitable solvent to dissolve the desired CaHizSa compounds and leave behind unreacted sulfur and impurities. Among such solvents may be mentioned diethyl ether,rchloro form, carbon tetrachloride, and benzene. The solution is ltered to remove the undissolved material and the filtrate is cooled to a temperature low enough to precipitate or crystallize the orange crystals of CsHizSs. The CaHizSs compounds are considerably less soluble in parafi'inic hydrocarbons than in the solvents mentioned above. Therefore, before cooling the solution, it is preferable to add a paraiiinic hydrocarbon, e. g. pentane, butane, hexane, isopentane, etc., to the solution to lower the solubility of the CsHlzSs compounds. They can then be precipitated at a somewhat higher temperature than if the parafiinic hydrocarbon is not added. The partially purified product so obtained usually has a melting range of between about 40 and 55 C.

The yields of CsH12S3 recorded in the tables and elsewhere in subsequent portions of this specification refer to the weight of the partially purified product obtained in the manner described. The percentage yields of CsHizSs are calculated using the weight obtained of the partially purified product and the weight of ICII12S3 which. is theoretically expected to be obtained on the basis of the amount of sulfur charged in the process.

The partially puried product can be used in many ways, for example as a cutting oil additive, a octane-number improver, a chemical intermediate for the production of acids, etc. How.- ever if a highly purified product is needed, the partially purified product can be further purified as by washing and recrystallization to obtain a mixture consisting essentially of the two isomers Y of CHlzSa having melting points of C. and 87 C., respectively. This purified mixture, whichv melts in a temperature range of between about 50 and 70 C., has many uses similar to those of the partially purifiedV product, and is especially many purposes the mixture may be lemployed in lieu of either of the pure compounds alone and in some instances it may even be preferred, as for example when used as an additive in certain petroleum fuels. However, when it is desired to obtain the pure isomers, they may be separated',

by taking advantage of their differences in solubility. The higher melting isomer is slightly less soluble in most organic solvents than the lowmelting compound, and accordingly it may beV isolatedby repeated crystallizations from organic f Y j solutions while the low-melting compound is rei covered from thefmother. liquor. Chloroform'is an.exampl'e:v of.- a solventi-:having superior. differentiallvsolvent; power' for. the. Vtwo isomersv One; specific: embodiment of'our' invention is described in the-'following example;

EXAMPLE The. sulfurization of di-isobutylenei was carriedout' in, an 1830 milliliter.' lead-lined autoclave which was providedwith inlet and outlet lines similarly, as shown in-Figure1 of thevdrawing.` 'IrhelA autoclave' was charged with: 160 grams of sulfur ('gram-mols). The sulfur was heated to 210 C-.and maintained atthat temperature while pumping liquid-.di-isobutylene into the-v autoclave nearthe bottom thereof below the surface. of the molten sulfur. 118- grams of di-isobutylene (1.05 gram-mols) were charged to the autoclavey over aperiod-of 30 minutes. The pressure inthe-autoclavefwas allowed to build"t up to 60= poundsl per squaref inch and'vWas-rmaintamed' at-'that'levelfby releasing hydrogen sulde at av regulated rate through a-pressurecontro1 valve inthe hydrogen sulcle` outlet line. Thereactants were main-`- tained inthe autoclave at'the temperature of 210 Cf.. andthe4 pressurefof 60 pounds?- per. square inch for 120 minutes beyondv theinitial 30minute period of charging. di-isobutylene'.' The: hydrogen suliide. formedK in the reaction-beyond that nec-- essary to,` maintain the.` desired pressurev was u was desired to.' obtain' the partially purified' Cal-112553..- compounds and therefore'thecrude Aproductwas treated with about' 0.75 liter of: diethyll ether. extraction treatment dissolved. out allo;fI the CsHizSa andleft behind thetunrea'cted; sulfur. The sulfurwas ltered off. a'nd .tor thef ltrate'was addedv aboutI 0;'154 liter. of? pentanei; s

The-resulting mixture was then cooledmtdryicef' and: acetone to #70 C.` whereuponA the vCaHizSy separatedout-` asA orangecrystals which` were? iiltered, washed twice with a cold (-7.0% 6.1).'. pentane-ethersolution,v and:V dried'r. Ther product thus obtained@ comprisedv amixturel'ofcthe' 8098s meltingpoint -a-nd the 871 C; melting point'isomersf of GsHizSsand' hadf'az melting'range 'of' between. about50c andf55 C., Tlieyieldzwasi791`2 per. cent` based on theamount of sulfureharged': 7.5gramsf of unreacted sulfur was found.

In they abover example; .wei-have describe'dan embodiment 'of our process. iniwhiclrcertain spe-- ci'camounts ofmaterialswere? used.: If: it is;J desired. to*- operate the process'oni a;danger-` stale;`V larger amounts of the.materialsimaymeusedfandl preferably in proportion'ssimilar."totlrioseused? inzthe example;

We have. conducte'clicomparativetests'-to show' the-'.advantages-of our new procedure-over closed:l vessel methcdg of performingthesesulfur-s zationreact-ions.v The" sulfuriz'ation of'di=i`so`1v *Y Weight j of Remarks' Pz'ior'process' 'Oui'.p'rocess. Priorprocess.4 Our'process'.'

wenn.

The times listed do uotinclude the initial'30-minute`period during which di=isobutylene-wes charged tothe reactor; From the aboveI table it can be seen that the yield of CaHizS` was markedlyv higher when the reaction wascarried-out'in the manner of the present invention for both' temperatures studied.

Itmay be' notedirr Table I that the-yields in both 3- (prior method) and run 4- (our method) were considerablyl lower than the yields inv either run 1" or run-'2. The lowA yields in runs 3 andt 4 areV due` to the-shortness of the' reactionperiod which was only 30 minutes' beyond the charging period andv to' the 'lower' temperatures employed as indicated in' the table: 'I'heA sigm'cant thing" to' observe' about 'these' two` runs is that although bothrunsv produced low'yields because V0i? th'e'short -reaction' periods and lower' temperatures,` run' 4; conducted'Y accordng to our' process, produced a considerably higher yield; than run 3' conducted according' to the' prior' process;

The reaction'temperature'is an important variable of the' presentv process, and we have dis'- covered'that an optimum temperature'of between about`200 and' 230"C', should' b`e` used in combina'tion with thecptimum pressure and'operat'- Y TableA II below records tlfle'resultsiof'te'sts which' showA the advantagesiobtain'edwhen using a reaction temper-atureof'aboutl" C2 In' these tests'di-i'sobutylene was' sulfurzed'a't different' temperatures while V f theotheroperatingjvariables ofthe process were maintained substantially constant. The proeed'ure'infthe tests wassubstantially the same as. describedin the example above and theres/uitsare as follows:

TablaII Run'f l`e1.np.,4 Pressure; Time- Weight of f Yield of.'

o- CsHxzSs; CsH'mSs No. C. i p. s.1.g. n mms.1 l gum percent' 5.....u 18o, 55k 24o w 55,4; i aan; 6; 21o` seV 120j 161.7 79.2' 7-.---- 241)-- 60' l2()l 141; 82r 2 69.75

l The times listedfdo not include the lminute dilisobutylenecharging period.

2 The crude-reactiomprodnct was-'offpoor quality, being tar-like. although;somewhatncrystallme.- The recoveredvCHnSa (i. e. the partially purified product) was very dark in color instead of thev desired light orange color.'

From@ the'V results infY TableA II.. it can be1 seen: thatra temperature offabout 210 C. produces` a'. higher yieldandi purer' quality! ofxtlfiedesired. CHieSra (in: theff'ormof the partially. puried;

product) than do the temperatures'abovef and,

9 range for our process is between about 200 and 230 C.

I'he reaction pressure also is an important variable in our process. It must be high enough to keep di-isobutylene in the liquid state but must be low enough to prevent appreciable solubility of hydrogen sulde in the reaction mass.. We have discovered that an optimum range for pressure of from about 25 to 120 pounds per square inch exists for the process. Both below and above this optimum range the yield of CaHizSs decreases. Furthermore, the product obtained when operating with pressures below the optimum range is of a poor and impure quality. We have conducted tests for reacting sulfur and di-isobutylene according to our process over a range of reaction pressures. for each test run was 210 C. and the reaction time 240 minutes after an initial charging period of 30 minutes. Di-isobutylene was charged in the amount of 1.05 mols per mols of sulfur. The results of these tests are recorded in Table III below.

1 Crude reaction product was tarry. Recovered CSHUSS (i..e., the partially purified product) was dark 1n color. The apparent high yield for Run No. 8 was due to inclusion of some'tarry matter 1n the partially purified product weighed. When this product was recrystallized the yield dropped to 51.7%. The product was still dark.

l HzS was held in the reaction vessel throughout the run.

From Table III it can be seen that the highest yield and purest quality of the desired CsHrzS3 product (in the form of the partially purified product) are obtained within the range of 25 to 120 pounds per square inch and preferably at about 60 pounds per square inch. This achievement of both a purer quality and a greater yield of desired product when operating at the specified pressures is an unexpected beneficial result of our invention.

In the foregoing description our process has been described as a batch-wise operation using equipment of the kind shown in Figure 1 of the drawings. However, it should be understood that our process is applicable also to continuous operation and can be performed in a continuous manner using equipment of the kind shown in Figure 3 of the drawing. The explanation of continuous operation of our process will be made by referring to Figure 3, in which is shown a reaction vessel l1 of structure similar to the reaction vessel I of Figure 1. Reaction vessel l1 is provided with a charge inlet I8, a stirrer i9, an inert gas inlet line 20, a thermowell 2l containing suitable temperature measuring means, and a hydrogen sulde release line 22 having a condenser 23, a pressure gauge 24, and a hydrogen sulfide release valve 25. Extending horizontally from the side of reaction vessel Il is a product take-off line 26. Line 26 draws offliquid product from vessel l1 in such a way as to avoid loss of gas from the system and consequent pressure drop. One way in which this can be accomplished is shown in the drawing. Line 26 leads into the top of a closed tank 21 having a The temperature'v line.

tween about 200 and 230 C. is maintained in thev liquid outlet 28 in its bottom. The liquid outlet is provided with a liquid level operated valve 29. Liquid product from reaction vessel I1 overflows from line 26 into the tank 21 and rises to a predetermined level in the tank. When the level of liquid exceeds the predetermined level, valve 29 in the bottom of tank 21 opens to release liquid and as the level drops, valve 29 closes until the level again builds up. The gas spaceabove the liquid level is connected by a line 30 to the gas space in reaction vessel l1 so that the pressure in reaction vessel Il and in tank 21 will be the same. With such an arrangement, there is a' gas seal formed in tank 21 so that only liquid is withdrawn and no pressure is l-ost in the reaction system.

To operate our process continuously, the procedure is as follows: A charge slurry is prepared from liquid di-isobutylene and sulfur with the amount of di-isobutylene being slightly in excess" of the stoichiometric amount of one mol per five mols of sulfur. This slurry is charged to reaction vessel I1 up to the level of the product take-01T The desired reaction temperature of bereaction vessel by heaters, not shown. When the reaction temperature is imposed on the mixture of di-isobutylene and sulfur, reaction takes place with the evolution of hydrogen sulfide which is released through the hydrogen sulfide release line at a rate such that the desired pressure of between about 25 and 120 pounds per square inch is maintained in the reaction vessel. The slurry of di-isobutylene and sulfur is charged continuously to the reaction vessel beneath the level of the liquid reaction mass in the vessel so that contact of di-isobutylene with hydrogen suliide is minimized.

The charge rate of the di-isobutylene-sulfur slurry (which is substantially equal to the product take-off rate) is regulated so as to give an average residence time for the individual molecules within the reactor equal to the desiredv length of the reaction period. The preferredlength of the reaction period in our` continuous operation -as in batch operation is between about and 180 minutes although shorter or longer periods can be used. To express the preferred length of the reaction period in terms of charge rate, the volume of reaction mass maintained in the reaction vessel (i. e. the volume of the reaction vessel up to the product take-off line) can be called a reaction mass volume. Then if one reaction mass volume of charge is introduced and one reaction mass volume of product is removed per hour, the length of the reaction period is one hour and the charge rate is one reaction mass volume per hour. Thus for the preferred reaction period length of between about 90 and 180 minutes or 1.5 and 3.0 hours, the charge rate is between about 2/3 and 1A; reaction mass volumes per hour. This is the preferred charge rate although ya faster or slower charge rate can be used if for any reason it is desired to rshorten or lengthen the reaction period. As a specific illustration we will consider the case of a reaction vessel having a capacity up to the level of the product take-off line, or in other words a reaction mass volume, of 50 gallons. A charge rate of 50 gallons per hour or one reaction mass vol-g ume per hour would correspond to a reaction period in batch operation of 60 minutes. A charge rate of 25 gallons per hour or 1/2 reaction mass volume per hour would correspond to a batch method reaction period of minutes.

In carrying out the sulfurization of di-isobutylemr by courprocess an` excess ofi the vdi-isobutylgenefabpye the#y stoichiometrirrv amount shouldE be Sadi A'.-considerable. increasein yieldof sulfur izedzproduct, over the yieldfobtained when using stci'chiometric; proportions isl obtained when ya slight excess of thedi-isobutylene is present. but there-.is no advantage in having more than about fper cent excess.

Qur processA has been described in its noncatalytic embodiment but it is also within the scope; of our invention to employ any suitable catalyst-for sulf-urization; as for example amines such.. as anisidine, benzyl paraphenetidiene, and their hydrosulfi'desor the crudesulfurization re.- action productitseli .may act as acatalyst..

. Theprocess ofonrinventionmay employ either oi the. isomers of difisobutylene, namely 2,4,4- trimethylpentene-L or. 2,4,4-trimethylpentene-2. The .same GsHieSs product is. obtained. when using either. one of these compounds-in the process of our. invention.

In describing the. process of our invention we havedl'stinguishedit from the .prior closed vessel method osulfurizi'ng di-isobutylene; For most practical purposes it is proper to .distinguish our process andthe prior process on the ground that the prior. processH is conductedV in a closedvessel. However, it should be understood that this distinotion isV based on a fundamental diierence in thetwo 'process in that the. prior processis conducted in such a manner that hydrogen sulfide i'sretained in the closed` vessel in contact withL the reactionmass whileour process is-conducted with removal of'- hydrogen sulfide from contact with the reaction mass substantially ask rapidly as; formed'. Thus it is conceivable that our process. in its lbroadlembodiments might be conducted in a closed vessel ii such vessel had a great volume ofspace-above the reactionmass so that hydrogen sulfide formed in the reaction could readily escape from the reaction mass into. the space above without being released from the closed vessel'.

priorclosedf-vessel method of' conducting these..

reactions. Our yields range upto about 80 per cent based'cn the-amount of sulfur charged. In addition4 our process-avoids vthe production ofsubstantial amountsof undesirable by-products such.

as themercaptans, disulfld'es, and polysuldes. Stillfurther; our-processpermits a divisobutylene-sulfur-ratio not far from stoichiometrical and'. thus-,permits considerablev savings in d-isobutyl-- ener Still further, our process operates. at` rela-- tively. low pressures so that expensive. heavy equipmentV is not required To all of. these advantages can be added thefact that our process produces the` desired. products in` high` purity.

We claim:

1. In\A a. processl for sulfurizing di-isobutylene` byl reacting di-isobutylene'with molterrsulfur, the improvement which comprises charging di-isobutylenebeneath:thefsurface oi a liquid reactionv masscompr-isingf molten sulfur'while maintaining If' the volume of the closed vessel,.the. pressure in the closed' vessel; and the amount of.

152 the: reactionsl mass at: a; temperature. ofbetween about 200o and 230 C. and a pressure of between about-25 and 12.0 pounds per. square. inch, and while removing hydrogen sulde formed in. the resultingreaction from contact with the reaction mass substantially asrapidly as formed.

2.,In a. process for sulfurizing difisobutylene by.y reacting. di-isobutylene with molten sulfur, the improvement which comprises charging di.- isobutylene f beneath the. surface of. a liquidreactionmass comprising molten sulfur over. a. charging periodof suiiicientjlength to. avoid. vaporizing the di-isobutylene. from. the. reaction mass while maintaining the. reaction.. mass at .a temperature ofbetween aboutl200 and230f CA andla pressure. of between about 25 and. .120.' pounds. per. square inch, while removing. hydrogen sul'de formed'. in the resulting reaction. from contact with. the reaction. mass substantially as rapidly as formed. and' maintaining. the reaction mass. under the reaction conditions for. a substantial period after the rate. of' formation oi'Y hydrogen sulfide. becomes very slow.

3. In a process for preparing compounds having the emperical fonmula Cal-11253 by reacting di-isobutylene with molten sulfur, the improvement which comprises charging di-isobutylene into. a reaction' vessel' beneath the surface of a liquid reaction masscomprising molten sulfur, in an amount ofY about l' molof cdi-'isobutylene perY 5-mols ofsulfur, while maintaining a temperature of between about 200 and 230 C. and a pressure; of between about 25 and l20-rpounds per squarel inch in said vessely and while removing hydrogenf sulfide formed in the resulting reaction from said vessel. substantially as rapidly as formed, maintainingsaid di-isobutyleneandsaid sulfur within said vessel. 'underthe reaction conditions for al period'cfv at least about 90 minutes including the time required for charging the di-isobutylene, and thereafter treating. the crude reaction. product with a solventto separa-tothe. CsthzSacom-V pounds from unreacted reactants f and. impurities.

4. In aprocess for. preparing compoundshaving the empirical. formula Cal-luso by. reacting di.-- isobutylene with molten. sulfunthe improvement whichcomprises changing diisobutylene into. a. reaction vessel. beneath the surface. of. a liquid reaction, mass comprising molten. sulfur., in an amount of slightly more than one. mol. of. di-isobutylene per 5 mols of sulfunwhile maintaining a temperature of between about. 200 and 2307" C. and a pressure of between. about 25.4 and 120. poundsper square inch in saidvessel', andwhil'e removing hydrogensulde. 'formed in the result.- ing reaction from. said' vessel' substantially as rapidly as formed, and at' the same time passing an inert gas through the reaction mass to aid in. hydrogen sulde removal' and to provide a partial pressureV of inert gas in the reaction vessel; maintaining saidA di-isobutylen'e. and said sulfur within said vessel underthe. reaction' conditions for a; period of1atleast about 90 minutes includ'- ing the time required for charging the di'iso` butyl'ene, andA thereafter'treating the crude reac- 'tion product with a .solvent to separate the CsHigSa compounds from unreacted. reactants and' impurities.

5. In. a process f'or sulurzi'ng di-isobutylene by reacting di-isobutylene` with molten. sulfur, the improvement which comprises continuously charging. difisobutylene as a liquid in admixture with. sulfur beneath the surfaceof a liquidr reactionmass comprising molten sulfur While main.- taining a temperatureof: between about. 200 and 230 C. and a pressure oi' between about 25 and 120 pounds per square inch in said vessel, and while removing hydrogen suliide formed in the resulting reaction from said Vessel substantially as rapidly as formed, and continuously removing crude reaction product from said vessel at a rate equal to the rate of charging di-isobutylene and sulfur to said vessel.

6. In a process for preparing compounds having the empirical form-ula CaHmSa by reacting diisobutylene with molten sulfur, the improvement which comprises charging said di-isobutylene as a liquid in admixture With sulfur in a ratio of slightly more than one mol of di-isobutylene per 5 mols of sulfur beneath the surface of a liquid reaction mass comprising molten sulfur, said mixture being charged to said Vessel at a rate of between about and 1/3 reaction mass volumes per hour, said charging being carried out while maintaining a temperature of between about 200 and 230 C. and a pressure between about 25 and 125 pounds per square inch in said Vessel and while removing hydrogen sulde formed in the resulting reaction from said vessel substantially as rapidly as formed, continuously removing crude reaction product from said vessel at a rate equal to the rate of charging di-isobutylene and sulfur to said vessel, and thereafter treating the crude reaction product with a solvent to separate the CsHmSa compounds from unreacted reactants and impurities.

DONALD R. STEVENS.

SAMUEL C. CAMP.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,450,658 Hansford et al Oct. 5, 1948 2,535,705 Stevens et al Dec. 26, 1950 2,535,706 Stevens et al. Dec. 26, 1950 OTHER REFERENCES Shepard et al.: J. Am. Chem. Soc., vol. 56, pp. 1355-6 (1934). 

1. IN A PROCESS FOR SULFURIZING DI-ISOBUTYLENE BY REACTING DI-ISOBUTYLENE WITH MOLTEN SULFUR, THE IMPROVEMENT WHICH COMPRISES CHARGING DI-ISOBUTYLENE BENEATH THE SURFACE OF A LIQUID REACTION MASS COMPRISING MOLTEN SULFUR WHILE MAINTAINING THE REACTION MASS AT A TEMPERATURE OF BETWEEN 